Distinction and prognosis of early arthritis phenotypes: an analysis in three European cohorts

OBJECTIVES: The objective of this study is to evaluate whether there are differences in the long-term prognosis across various phenotypes of early arthritis (EA). METHODS: Three EA cohorts (Reade, Etude et Suivi des Polyarthrites Indifférenciées Récentes (ESPOIR) and Early Arthritis Clinic (EAC)) were analysed. Clinical data were collected up to 24 years. Hands and feet radiographs were scored according to the Sharp van der Heijde (SvdH) method. Latent class analysis was applied to determine the EA phenotypes at baseline. Each class received a label reflecting its most prominent features. Prognostic outcomes included Health Assessment Questionnaire (HAQ), Short Form 36 (SF36) and SvdH score. The association between class membership and outcomes over time was tested in multivariable models. RESULTS: In total, 390 (Reade), 798 (ESPOIR) and 3991 (EAC) patients were analysed separately. Two classes with symmetrical polyarthritis emerged; one of these labelled as autoimmune inflammatory polyarthritis (AIPA), had high likelihood of acute phase reactants (APR) elevation and autoantibody positivity, while the other (mild-inflammatory polyarthritis; MIPA) had not. A third class had oligoarthritis of upper limbs (OAUL) and could be subdivided into autoimmune OAUL and mild-inflammatory OAUL. A fifth class had oligoarthritis of lower limbs. The SvdH scores were worse in patients with APR/autoantibodies (AIPA) than in those without (MIPA). No clinically meaningful differences across classes in HAQ or SF36 over time were found. CONCLUSION: Radiographic progression over time primarily occurs in EA patients with APR/autoantibodies. The absence of these markers, however, does not necessarily translate into better long-term function and quality of life. Clinicians should not only aim at preventing joint damage, but look beyond structural progression in order to further improve the lives of people with EA.